A083059 a(n) is the number of natural numbers k such that A078496(k)=n.

1, 0, 2, 0, 0, 0, 3, 0, 2, 0, 0, 0, 3, 0, 3, 0, 0, 0, 3, 0, 0, 0, 0, 0, 3, 0, 5, 0, 0, 0, 0, 0, 3, 0, 0, 0, 5, 0, 4, 0, 0, 0, 3, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 3, 0, 6, 0, 0, 0, 0, 0, 4, 0, 0, 0, 5, 0, 4, 0, 0, 0, 0, 0, 4, 0, 0, 0, 5, 0, 0, 0, 0, 0, 4, 0

Offset: 5

Author

Serhat Sevki Dincer (sevki(AT)ug.bilkent.edu.tr), Apr 18 2003

Keywords

• easy
• nonn

Examples

			a(19)=3 since there are only k=13,16,18 for which A078496(k)=19
		

Crossrefs

Cf. A078496.

Programs

PARI

b(n)={forprime(p=nextprime(n+1), 2*n, if(isprime(2*n-p), return(p))); 0}
a(n)={if(isprime(n), sum(i=n\2+1, n-1, b(i)==n), 0)} \\ Andrew Howroyd, Nov 06 2019

Formula

a(n) = #{k: k>3 integer; A078496(k)=n}.

Extensions

Terms a(24) and beyond from Andrew Howroyd, Nov 06 2019